The Farallons are a granitic formation that is part of the Farallon Ridge. Shallow soils can be found scattered on some of the south Farallons. Vegetation is dominated by Farallon weed, an important nest-building material for cormorants and gulls. Wildlife populations were heavily exploited in the late eighteenth and early nineteenth century for meat, hides, and eggs, and overfishing reduced seabird food supplies in the mid-nineteenth century.